Phase-inverting translating circuit



2,830,133 PHASE-INVERTING TRANSLATING ClRCUlT John E. Ranks, Walnut Creek, Califi, assignor to General Electric Company, a corporation of New York Application April 29, 1952, Serial No. 284,902

16 Claims. (Cl. 119-471 I My invention relates to translating apparatus and, more particularly, pertains to an improved circuit for deriving an undulating potential corresponding to an applied Such'a cir-v undulating potential, but inverted in phase. cult is especially useful in an application wherein from an unbalanced or single-ended source, i. e., one supplying an undulating potential having'its alternating potential axis displaced from a plane of fixed reference potential, there is derived an undulating potential that is balanced relative to the reference potential. For couvenience my invention will be described in that connection.

As used herein, the term balanced refers to an arrangement of the push-pull type in which a pair of undulating potentials of the same Wave form are supplied to a utilization circuit with equal amplitude, but of opposite phase, at every instant of operation.

his a general object of my invention to provide an improved phase-inverting translating circuit.

Another object of my invention is to provide a phaseinverting translating circuit which may be employed for effectively converting a single-ended source of undulating potential to a push-pull source and which afiords output potential amplitudes greater than heretofore attainable. I

It is a further object of my invention to provide a phase-inverting translating circuit incorporating a'self-.

balancing feature for assuring a balanced output potential in response to an applied unbalancedinput potential of variable amplitude.

Briefly stated, a phase-inverting translating circuit in accordance with my invention comprises first and second electron discharge devices each including an anode, a cathode and a control electrode. A common anodecathode current path is provided for connecting the discharge devices in series. A cathode impedance for the first device and an anode impedance for the second device are included in this path. The circuit' further includes another impedance having one terminal coupled to the cathode of the first device, another terminal coupled to the anode of the second'device and a portion intermediate the terminals coupled to the control electrode of the second device. A control electrode-cathode circuit for the firstdischarge device is provided for applying an undulating input potential to that device, and an output circuit including the anode impedance, 'isprovided for ,deriving an undulating output potential from the second device corresponding to the input potential, but inverted in phase. t i V The novel features, believed to be characteristic of the present invention, are set forth with particularity in the appended claims. The invention itself, however, both as to its. organization and method of operation, together with, further objects and advantages thereof, may bestbe understood by referenceto the following description taken in connection with. the accompanying drawing in which:

Fig. l is a schematic circuit diagram of a phase-invert ing translating circuit constructed in accordance with my invention; and

Fig. 2 illustrates another embodiment of my invention. With reference now to Fig. 1, there is shown, schematically, a circuit diagram of a phase-inverting translating circuit 10, constructed in accordance with the instant or grid 14, and a second electron discharge device 15, having an anode 16, a cathode 17 and a control electrode 18. Cathode 13 is connected through a cathode impedance 19, preferably a resistor, to the negative terminal of a sourceof potential 20, the positive terminal of which is" grounded. Anode 12 is directly connected to cathode 17,

' and anode 16 is'connectaed through an anode impedance 21, also preferably a resistor, to the positive terminal of.

another source of potential 22, the negative terminal of which is grounded. Resistors 19 and 21 thus are included the junction of resistors Band 24 to ocntrol electrode 18' of device 15. a

A control electrode-cathode circuit for discharge device 11 includes a resistor 26 extending between control electrode 14 and the variable tap of a potentiometer 27 connected in parallel with source 20. The tap of potentiometer 27 is by-passed to ground by a condenser 28. In order to apply an undulating input potential to device 11, a source 29, such as a generator of sawtooth or sweep waves, is coupled to control electrode 14 through a coupling condenser 30 and appropriate ground connections.

The output oftranslator circuit 10 includes cathode impedance 19 and anode impedance 21, and for deriving undulating output potentials therefrom, a pair of coupling condensers 31 and 32 extend from cathode 13 and anode 16,-respectively, to a utilizationcircuit such' as deflection plates 33 of a cathode-ray tube 34;

In constructinga translating circuit in accordance with the present invention, it has been found desirable to utilizeelectron tubes 11 and 15 which have essentially the same dynamic anode-cathode impedances and to have resistors 19 and 21 0f substantially equal Values. Also, the resistance value of resistor'24 should be slightly larger than that of resistor 23 to provide a suitable control gridto-cathode bias potential for tube 15. However, in some applications, equal resistance values have been found to be satisfactory for resistors 23 and 24. A potentiometer 27 is provided in parallel with source 20 having a tap which is adjusted to provide a suitable grid-bias potential for tube. 11. i V

In considering the operation of the circuit shown in Fig. 1, it'isassumed that generator'29 supplies an uncordance with the invention, may be represented by saw-v tooth wave forms 36 and 37. It is further assumed that the undulating potentials applied to the input circuits of tubes'll and 15. are not so large in magnitude as to effect grid: currentflow 01' anode current cut off. In' otherwords, the tubes are operated essentially as linear:

devices. I From an inspectionof Fig.

be the same, since there is no alternative current path,

l'it is apparent that tube 15 is in an anode-load circuit fortube'll, and'thattub'e" 11 is in a cathode-load circuit for tube 15, Consequently, the anode-cathode current of thesetubesiriust art circuit,v

Responsive to undulating potential 35,- here derived at load impedance 19 of tube 11, the sawtooth wave 36 t which corresponds in phase to the applied wave 34. Be-

cause the anode-cathode current paths of tubes 11 and 15 are in series, the current .variations which produce poten rent variations in theseries circuit. Hence, there is derived from anode load 21, the output voltage of wave and 37. ofcqual amplitude are supplied tolload. 33. For

this analysis, let it be assumed for the (moment that the impedance values presented by,devices name 15 are unequal, with that of device .11 the higher of. the two. For such a condition to exist, the grid-cathode potential of tube 11 should be larger, in a negative sense, than the corresponding potential of tube 15. I However', the anodecathode current of these tubes must beequal and the re sulting voltage drop between the anode and cathode of tube 11 should be correspondingly larger than that of tube 15. Hence, anode 12 (and cathode.17) must be more positive relative to grid 18 than originally assumed, i. e., the grid-cathode potential of tube 11 should be the larger in a negative sense, than that for tube 15 which.

is contradictory to the initially assumed conditions. It is evident then, that the initial assumption is invalid. i

From the foregoing non-sequitur, it may be concluded that in operation, the grid biases for tubes 11 and 15 and their dynamic impedances are substantially equal at all times. With such a relationship, the output potentials 36 and 37, although of opposite polarity, have the same magnitude from instant to instant. If this latter condition does not hold true, and an. unbalance does exist, for example, as a re su1t in a'shift of dynamic impedance of one tube, for example, due, to large variations in input amplitude or tubeaging, the resulting potential applied to'cathode 17 is in a direction and nfamagnitude to equalize the dynamic impedances. and restore, the balance condition. 1 9

It may be appropriate to point out that a change in static grid bias level in tube 1,1,. etfected by displacing tap 27, also alters the biasfor tube 15. .Thisis evident from the preceding discussion of dynamic operation, wherein it was shownthat because the dynamic impedances of the tube must remainthe same at all times, the grid biases must be equal. v

Thus, it may be seen that iuresponse to unbalanced saw-tooth wave 35, a push-pull undulating potential is supplied to deflection plates 33 of cathode ray tube.

'The alternating potential axis of this undulating voltage remains at a g iven reference value to providera balanced wave for a variety of circumstances .-which, in conventional circuits, might cause an unbalance'to occur. V

In practice, it has been found that becausetubes 11- and 15 are -in series a total anode suppl y potential equal the sum of the maximum rated voltage for each tube may be employed and outpunamplitudesup to 100% greater than that available in asingle tube, prior art, phase inverter circuit may be derived ataeach of impedances 19 and21. Hence, it is evident that aphaseinverting translating circuit in accordance, with my invention r'epresents a rn'aterialgirnprovement over that prior The embodiment of In yv inventionl represented 'inFig. 2,

provides a circuit amplification much nearer unity than that of the circuit illustrated in Fig. 1. Translating circuit 10, in accordance with the invention, is essentially like circuit 10 of Fig. l and similar elements are represented by the identical reference numerals. Instead of the triode type electrode tubes 11 and 15, pentode type tubes 11' and 15' are employed. These tubes include, in addition to the usual anode, control grid and cathode, a screen electrodeor grid 50 and a suppressor electrode 51, in tube 11, and a screen grid 52 and a suppressor grid 53in tube 15'. Resistors 23 and 24 are represented as a single resistor havinga tap 54, inter mediate its end portions connected to control grid 18 of tube15'; A tap 55 of resistor 23--24 intermediate tap 54 and the end portion thereof connected to anode 16 is connected'to screen grid 52 of tube 15. Screen grid 50, of tube 11, is connected to a third tap 56 of resistor 2324, disposed intermediate taps 54 and 55. The suppressor grids 51 and 53 of the tubes are connected to the respective cathodes thereof. A condenser. 57 extends between control electrode 18 and cathode 13, and a pair of utilization circuits 58 and 59 are coupled to cathode impedance 19 and to anode impedance 21, respectively In constructing a signal-translating circuit 10, as shown in Fig. 2, the sa'meconsiderations applied to Fig. l are carried out. In addition, taps 55 and 56 are adjusted to provide the required screen grid potentials for tubes 11' and 15,'and the value of condenser 57 is chosen to cornpensate for tube and stray capacitances.

The operation of this embodiment of the invention generally follows that presented in connection with Fig. l. A source 58 supplies an undulating potential, for example, of sinewave form 59, to the control grid circuit of tube 11. In response to the applied Wave, an in-phase undulating potential 60,is developed at impedance l9 and supplied to a utilization circuit 61. At the same time, an out-of-phase potential 62 is derived, at impedance 21 and applied to another utilization circuit 63.

Condenser 57, as a result of its relationship in the circuit operates to balance out undesirable tube and stray' capacitances, insofar as signal currents resulting from such capacitances are concerned. Specifically, such undesirable capacitances tend to reduce the amplitude of high frequency components in the translated undulating signal.v By selecting the value of condenser 57 so that its impedance becomes low for these frequency components, potential variations are transferred from cathode 13 of tube 11 to grid 18 of tube 15'. The phase is such as to augment current variations in tubes 11' and 15" at the frequencies under consideration and thereby compensate any tendency toward a reduction in amplitude.

Inaddition to having the same advantages as enumerated for the circuit of Fig. 1, thisembodiment of the invention .is characterized by greater'output single amplitudes, because of its near unity gain due to higher transconductance of the pentode-type tube. Moreover, a great degree, of circuit isolation is afforded between load circuits 61- and 63 because of the added series capacitance provided by tube 15 as compared with prior single-tube circuits. 7 t

While particular embodiments of my invention have been shown and described, it is to, be understood that various changes and modifications may be made without departing from thisinventionin its broader aspects, and, therefore, the aim in the appended claims is' to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secureby Letters 'Patent of the United States is:

. l. -A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode and a control electrode, a common anode-cathode curr'entpathfor-said devices connecting said devices in series and including a cathode impedance forsaid first device and ananode impedance for said trode-cathode circuit for said first device for applying an undulating input potential to said first device, and an output circuit including said anode impedancev for deriving an undulating output potential'from said second device corresponding to said input potential but inverted in phase.

2. A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode and a control electrode, a common anode-cathode current path for said devices connecting said devices in series and including a cathode resistor for said first device and an anode resistor for said seconddevice, another resistor having a first terminal directly connected to said cathode of said first device and a second terminal of said impedance directly connected to said anode of said second device and a portion intermediate said first and second terminals coupled to said control electrode of said second device, a control electrode cathode circuit for said first device for applying an undulating input potential to said first device, and an output circuit including said anode resistor for deriving an undulating output potential from said second device corresponding to said input potential, but inverted in phase.

3. A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode and a control electrode, a common anode-cathode current path for said devices connecting said devices in series and including a cathode impedance for said first device having a given value and an anode impedance for said second device having a value substantially equal to said given value, another impedance having a first terminal directly connected to said cathode of said first device and a second terminal of said impedance directly connected to said anode of said. second device and a portion intermediate said first and second terminals coupled to said control electrode' of said second device, a control electrode-cathode circuit for said first device for applying an undulating input potential to said first device,'and an output circuit including said anode impedance for deriving an undulating output potential from said second device corresponding to said input potential, but inverted in phase.

4. A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode and a control electrode, a common anode-cathode current path forsaid devices connecting said devices in series and including a' cathode impedance for said first device having a resistive component of a given value and an anode impedance for said second device having a resistive component of avalue substantially equal to said given value, another impedance having a first terminal directly connected to said cathode of said first device and a second terminal directly'connected to said anode of said second device and a portion intermediate said first and second terminals coupled to said control electrode of said second device, a control electrode-cathode circuit for said first device for applying an undulating input potential to said first device, and an output circuit including said anode impedance for deriving an undulating output potential ,from said second, device corresponding to said input potential, .but inverted in phase. Y

5. A phase-inverting translating, circuit comprising firstand second electron discharge devices each including an anode, a cathode and a control electrode, a com mon anode-cathode current pathgfor said devices connecting said devices in series'and including a cathode impedance for-said first device and an anode impedance for said second device, a first resistance having one of its terminals directly connected to said cathode of said first device, a second resistance having one of its terminals directly connected to said anode of said second device, a conductive connection extending among the remaining terminals of said first and second resistances and said control electrode of said second device, a control electrodecathode circuit for said first device for applying an undulating input potential to said first device, and an output ing an anode, a cathode and a control electrode, a common anode-cathode current path for said devices connecting said devices in series and including a cathode impedance for said first device and an anode impedance for said second device, a first resistance of a given value having oneof its terminals directly connected to said cathode of said first device, a second resistance of a value at least equal to said given value having one of its terminals directly connected to said anode of said second device, a conductive connection extending among the remaining terminals of said first and second resistances and said control electrode of said second device, a control electrode-cathode circuit for said first device for applying an undulating input potential to said first device, and an output circuit including said anode impedance for deriving an undulating output potential from said second device corresponding to said input potential, but inverted in phase.

7. A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode and a control electrode, said devices having substantially equal dynamic anode-cathode impedances, a common anode-cathode current path for said devices connecting said devices in series and including a cathode impedance for said first device and an anode impedance for said second device, another impedance having a first terminal directly connected to said cathode of said first device and a second terminal directlyconnected to said anode of said second device and a portion intermediate said first and second terminals coupled to said control electrode of said second device, a control electrode cathode circuit for said first device for applying an undulating input potential to said first device, and an output circuit including said anode impedance for deriving an undulating output potential from said second device corresponding to said input potential, but inverted in phase.

8. A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode and a control electrode, a common anode-cathode current path for said devices connecting said devices in series and including a cathode impedance for said first device and an anode impedance for said second device, another impedance having a first terminal directly connected to said cathode of said first device and a second terminal directly connected to said anode of said second device and a portion intermediate said first and second terminals coupled to said control electrode of said second device, a control electrode-cathode circuit for said first device for applying an undulating input potential to said first device, a first output circuit including said cathode impedance forderiving an undulating output potential from said first device corresponding to said input potential, and a second output circuit including said anode impedance for deriving another undulating potential from said second device corresponding to said input potential, butinverted in'phase.

. 9. A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode and a control electrode, a common anode-cathode currentpath for said devices connecting said devices in series and including a'cnthode impedance for said first device and an anode impedance for said second device, another impedance having a first terminal directly connected to said cathode of said first device and a second terminal directly connected to said anode ofsaid second device and a portion intermediate said first and second terminals coupled to said control electrode of said anode-cathode current path for said devices connecting said devices in series and includinga cathode impedance for said first device and an anode impedance for said second device, another impedance having a first terminal directly connected to said cathode of said first device and a second terminal directly connectcd'to said anode of said second device and a portionintermediate said first and second terminals coupled to said control'electrode of said second device, a control electrode-cathode circuit for said other conductive connection extending from said screen electrode of saidfirst device to a'third'tap of said resistive impedance intermediate 'said'firstland second taps thereof, a control electrode-cathode circuit for said first device for applying an undulating .input potential to said first device, andian output circuit including said anode impedance for deriving an undulatingoutput potential from said second device corresponding to said input potential, but inverted in phase. l

13. In. combination a first and second electron discharge device each including an anode, cathode and a first device forapplying an undulating input potential to said first device, an output circuit including saidanode impedance for deriving an undulating output potential from said second device corresponding to said input po' tential, but inverted in phase, and a capacitance having one terminal coupled to said cathode of said first device a and another terminal coupled to said control electrode of said second device for compensating undesirable capacitances in said translating circuit.

ll. A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode, a control electrode, and an additional electrode, a common anode-cathode current path for said devices connecting said devices in'series and including a cathode impedance for said first device and an anode impedance for said second device, another impedance having a first endtermi al directly, connected to said cathode of said first device and a second end terminal directly connected to said anode of said second device, a first portion intermediate said first and second ter-" minals coupled to said control electrode of said second device, .a second portion intermediate said first portion and said second terminal coupled to said additional electrode of said second device and a third portion intermediate said 'first and second portion coupled to said additional electrode of said first-device, a control electrodecathode circuit for said first device for applying an undulatinginput potential to said first device, and an output circuit including said anode impedance for deriving an undulating output potential from said second device corresponding to said input potential, but inverted in phase.

12. A phase-inverting translating circuit comprising first and second electron discharge devices each including an anode, a cathode, a control electrode, and a screen electrode, a common anode-cathode current path for said devices connecting said devices in series and including a cathode impedance for said first device and anan'ode impedance for said second'device, another essentially resistive impedance having a first'end terminal-dircctlyconnected to said cathode of said first device, a second end terminal directly connected to said anode of said second device, a conductive connection extending from said control electrode of said second device to'afirst tap-of said resistive impedance intermediate said first and sec nd endterminals thereof, another conductive connection extending from said s'ereen 'electrode of said second device to a second tap l'ot's'aid resistive impedance "intermediate said second end terminal and said first tap thereof, still an correspondingto said input signal.

control electrode, a common anode-cathode current path for said devices connecting said devices in series and including a cathode impedance for saidfirst device and an anode impedance for said second device, anther impedance having a first terminal directly connected to said cathode of said first device and asecond terminal of said impedance directly connected to said anode of said second device and alportion intermediate said first and second terminals coupled to said control electrode of said second device, a control electrode-cathode circuit for said first device 'for applying an undulating input potential to said first device, a first outputcircuit including said anode impedancefor deriving an undulating'output potential from said second device corresponding to said input potential'but inverted in phase, and a second output cir-. cuit including said cathode impedance for deriving an undulating'output potential from said first device corresponding to said input'potential.

14. In combination a first and second electron discharge device each including an anode, cathode and a control electrode, a common anode-cathode current path for said devices connecting said devices in series and including a cathode impedance for said first device and an anode impedance for said secondfldevice, another impedancehaving a first terminal directly connected to said cathode of said first device and a second terminal of said impedance directly connected to saidanode of said second device and a portion intermediate said first and second terminals coupled to said control electrode of said second device, a control electrode-cathode circuit for said first device for applying an undulating input signal to said first device, means for deriving a first undulating output signal from said second device corresponding to said input signal but inverted in phase, and means for deriving a second undulatingoutput signal from said first device 15. In combination a first and second electron discharge device each including an anode, cathode and a control electrode, a common anode-cathode current path for said devices connecting said devices in series and including a cathode impedance for said first device and an anode impedance for said second device, a control electrode-cathode circuit for said first device for applying an undulating input signal to said first device, another impedance having a first terminal connected to the junction of said anode impedance with said anode of said second device and a second terminal connected to the junction of said cathode impedance with said cathode/of said first device, and a portionintermediate said first and second terminals coupled to said control electrode of said second device, means for deriving a first output signal from said cathode of said first device and means for deriving a second output signal from said anode of said'second device.

16. In combination a first and second electron discharge device each'including :an anode, cathode and a control :electrode, a common anode-rcathode current path for said devices connecting said devices in seriesand including acathode impedance for said first device and an anode impedance for said second device, a control elec trode-cathode circuit lfo'r said first device for applying an undulating-input signal to said first dcvicodneansfor deriving signal variations' from the anode of said second device, means for deriving signal variations from the cathode of said first device, a resistance having first and 2,592,193 Saunders Apr. 8, 1952 second terminals and a third terminal intermediate said 2,631,197 Vilkomerson et al Mar. 10, 1953 first and second terminals, means for applying said anode signal variations to said first terminal, means for applying R G TS said cathode signal variations to said second terminal, 5 427 334 Great Britain 7 1 5 means coupling said third terminal to said control elec- 439 4 Great Britain J l 22, 3 trode of said second device, means for deriving a first output signal from said first terminal and means for OTHER REFERENCES deriving a second output signal from said second terminal. Text Vacuum Tube Amplifiers by valley and Wanamn 10 References Cited in the file of this patent gfggf i ig Senes Pages UNITED STATES PATENTS Electronics, Stable Instrument Amplifier by Peter C. 2,438,960 Blitz Apr. 6, 1948 Sulzer, page 116, March 1950.

2,474,435 Moore June 28, 1949 

